user
Below is an instruction that describes a task, paired with an input that provides further context. Write a response that appropriately completes the request.

### Instruction:
Calculate the frequency of letter ‘a’ in the following sentence

### Input:
This is a sentence

### Response:
assistant
The letter 'a' appears twice in the sentence. The frequency of letter 'a' is therefore 2 / 13 (or 15.38%).